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Viral Replication
Viral replication is the formation of biological viruses during the infection process in the target host cells. Viruses must first get into the cell before viral replication can occur. Through the generation of abundant copies of its genome and packaging these copies, the virus continues infecting new hosts. Replication between viruses is greatly varied and depends on the type of genes involved in them. Most DNA viruses assemble in the nucleus while most RNA viruses develop solely in cytoplasm. Viral production / replication Viruses multiply only in living cells. The host cell must provide the energy and synthetic machinery and the low-molecular-weight precursors for the synthesis of viral proteins and nucleic acids. Virus replication occurs in seven stages: # Attachment # Entry (penetration) # Uncoating # Replication # Assembly # Maturation # Release (liberation stage). Attachment It is the first step of viral replication. Some viruses attach to the cell membrane of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virus
A virus is a submicroscopic infectious agent that replicates only inside the living Cell (biology), cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity. Since Dmitri Ivanovsky's 1892 article describing a non-bacterial pathogen infecting tobacco plants and the discovery of the tobacco mosaic virus by Martinus Beijerinck in 1898, more than 16,000 of the millions of List of virus species, virus species have been described in detail. The study of viruses is known as virology, a subspeciality of microbiology. When infected, a host cell is often forced to rapidly produce thousands of copies of the original virus. When not inside an infected cell or in the process of infecting a cell, viruses exist in the form of independent viral particles, or ''virions'', consisting of (i) genetic material, i.e., long ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Baltimore Classification System
Baltimore classification is a system used to Virus classification, classify viruses based on their manner of messenger RNA (mRNA) synthesis. By organizing viruses based on their manner of mRNA production, it is possible to study viruses that behave similarly as a distinct group. Seven Baltimore groups are described that take into consideration whether the viral genome is made of deoxyribonucleic acid (DNA) or ribonucleic acid (RNA), whether the genome is single- or Double-stranded RNA, double-stranded, and whether the Sense (molecular biology)#RNA sense in viruses, sense of a single-stranded RNA genome is positive or negative. Baltimore classification also closely corresponds to the manner of Viral replication, replicating the genome, so Baltimore classification is useful for grouping viruses together for both Transcription (biology), transcription and replication. Certain subjects pertaining to viruses are associated with multiple, specific Baltimore groups, such as specific forms ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asymptomatic
Asymptomatic (or clinically silent) is an adjective categorising the medical conditions (i.e., injuries or diseases) that patients carry but without experiencing their symptoms, despite an explicit diagnosis (e.g., a positive medical test). Pre-symptomatic is the adjective categorising the time periods during which the medical conditions are asymptomatic. Subclinical and paucisymptomatic are other adjectives categorising either the asymptomatic infections (i.e., subclinical infections), or the psychosomatic illnesses and mental disorders expressing a subset of symptoms but not the entire set an explicit medical diagnosis requires. Examples An example of an asymptomatic disease is cytomegalovirus (CMV) which is a member of the herpes virus family. "It is estimated that 1% of all newborns are infected with CMV, but the majority of infections are asymptomatic." (Knox, 1983; Kumar et al. 1984) In some diseases, the proportion of asymptomatic cases can be important. For exam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Torque Teno Virus
''Alphatorquevirus'' is a genus of viruses in the family ''Anelloviridae'', in group II in the Baltimore classification. It encompasses numerous species of the virus known as TTV (transfusion-transmitted virus), torque teno virus, SENV (senior virus), SANBAN, and various other names. The genus contains 26 species. Taxonomy The genus contains the following species: * ''Alphatorquevirus cerco1'' * ''Alphatorquevirus cerco2'' * ''Alphatorquevirus cerco3'' * ''Alphatorquevirus cerco5'' * ''Alphatorquevirus cerco6'' * ''Alphatorquevirus cerco7'' * ''Alphatorquevirus homin1'' * ''Alphatorquevirus homin2'' * ''Alphatorquevirus homin3'' * ''Alphatorquevirus homin4'' * ''Alphatorquevirus homin5'' * ''Alphatorquevirus homin6'' * ''Alphatorquevirus homin7'' * ''Alphatorquevirus homin9'' * ''Alphatorquevirus homin10'' * ''Alphatorquevirus homin13'' * ''Alphatorquevirus homin14'' * ''Alphatorquevirus homin15'' * ''Alphatorquevirus homin17'' * ''Alphatorquevirus homin18'' * ''Alphatorquevirus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parvoviridae
Parvoviruses are a family of animal viruses that constitute the family ''Parvoviridae''. They have linear, single-stranded DNA (ssDNA) genomes that typically contain two genes encoding for a replication initiator protein, called NS1, and the protein the viral capsid is made of. The coding portion of the genome is flanked by telomeres at each end that form into Stem-loop, hairpin loops that are important during replication. Parvovirus virions are small compared to most viruses, at 23–28 nanometers in diameter, and contain the genome enclosed in an icosahedral capsid that has a rugged surface. Parvoviruses enter a host cell by endocytosis, travelling to the nucleus where they wait until the cell enters its replication stage. At that point, the genome is uncoated and the coding portion is replicated. Viral messenger RNA (mRNA) is then Transcription (biology), transcribed and Translation (biology), translated, resulting in NS1 initiating replication. During replication, the hairpi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circoviridae
''Circoviridae'' is a family of DNA viruses. Birds and mammals serve as natural hosts. The family has two genera. Diseases associated with this family include: PCV-2: postweaning multisystemic wasting syndrome; CAV: chicken infectious anemia. Structure Viruses in the family ''Circoviridae'' are non-enveloped, with icosahedral and round geometries, and T=1 symmetry. The diameter is around 20 nm. Genomes are circular and non-segmented, around 3.8kb in length. The capsid consists of 12 pentagonal trumpet-shaped pentamers. There are two main open reading frames arranged in opposite directions that encode the replication and capsid proteins. Life cycle Viral replication is nuclear. Entry into the host cell is achieved by penetration into the host cell. Replication follows the ssDNA rolling circle model. DNA templated transcription, with some alternative splicing mechanism is the method of transcription. The virus exits the host cell by nuclear egress, and nuclear pore expo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vertebrate
Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebrata with some 65,000 species, by far the largest ranked grouping in the phylum Chordata. The vertebrates include mammals, birds, amphibians, and various classes of fish and reptiles. The fish include the jawless Agnatha, and the jawed Gnathostomata. The jawed fish include both the Chondrichthyes, cartilaginous fish and the Osteichthyes, bony fish. Bony fish include the Sarcopterygii, lobe-finned fish, which gave rise to the tetrapods, the animals with four limbs. Despite their success, vertebrates still only make up less than five percent of all described animal species. The first vertebrates appeared in the Cambrian explosion some 518 million years ago. Jawed vertebrates evolved in the Ordovician, followed by bony fishes in the Devonian. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Poxvirus
''Poxviridae'' is a family of double-stranded DNA viruses. Vertebrates and arthropods serve as natural hosts. The family contains 22 genera that are assigned to two subfamilies: ''Chordopoxvirinae'' and ''Entomopoxvirinae''. ''Entomopoxvirinae'' infect insects and ''Chordopoxvirinae'' infect vertebrates. Diseases associated with this family include smallpox. Four genera of poxviruses can infect humans: '' Orthopoxvirus'', '' Parapoxvirus'', ''Yatapoxvirus'', ''Molluscipoxvirus''. ''Orthopoxvirus'': smallpox virus (variola), vaccinia virus, cowpox virus, Mpox virus; ''Parapoxvirus'': orf virus, pseudocowpox, bovine papular stomatitis virus; ''Yatapoxvirus'': tanapox virus, yaba monkey tumor virus; ''Molluscipoxvirus'': molluscum contagiosum virus (MCV). The most common are vaccinia (seen on the Indian subcontinent) and molluscum contagiosum, but Mpox infections are rising (seen in west and central African rainforest countries). The similarly named disease chickenpox is no ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adenoviridae
Adenoviruses (members of the family (biology), family ''Adenoviridae'') are medium-sized (90–100 nanometer, nm), nonenveloped (without an outer lipid bilayer) viruses with an icosahedral nucleocapsid containing a double-stranded DNA genome. Their name derives from their initial isolation from human adenoids in 1953. They have a broad range of vertebrate hosts; in humans, more than 50 distinct adenoviral serotypes have been found to cause a wide range of Adenovirus infection, illnesses, from mild respiratory infections in young children (the common cold) to life-threatening multi-organ disease in people with a Immunodeficiency, weakened immune system. Virology Classification This family contains the following genus, genera: * ''Aviadenovirus'' * ''Barthadenovirus'' * ''Ichtadenovirus'' * ''Mastadenovirus'' (including all human adenoviruses) * ''Siadenovirus'' * ''Testadenovirus'' Diversity In humans, currently there are 88 human adenoviruses (HAdVs) in seven species (H ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cancer
Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible Signs and symptoms of cancer, signs and symptoms include a lump, abnormal bleeding, prolonged cough, unexplained weight loss, and a change in defecation, bowel movements. While these symptoms may indicate cancer, they can also have other causes. List of cancer types, Over 100 types of cancers affect humans. Tobacco use is the cause of about 22% of cancer deaths. Another 10% are due to obesity, poor Diet (nutrition), diet, sedentary lifestyle, lack of physical activity or Alcohol abuse, excessive alcohol consumption. Other factors include certain infections, exposure to ionizing radiation, and environmental pollutants. infectious causes of cancer, Infection with specific viruses, bacteria and parasites is an environmental factor cau ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Transformation
Malignant transformation is the process by which cells acquire the properties of cancer. This may occur as a primary process in normal tissue, or secondarily as ''malignant degeneration'' of a previously existing benign tumor. Causes There are many causes of primary malignant transformation, or tumorigenesis. Most human cancers in the United States are caused by external factors, and these factors are largely avoidable. These factors were summarized by Doll and Peto in 1981, and were still considered to be valid in 2015. These factors are listed in the table. a Reproductive and sexual behaviors include: number of partners; age at first menstruation; zero versus one or more live births Examples of diet-related malignant transformation Diet and colon cancer Colon cancer provides one example of the mechanisms by which diet, the top factor listed in the table, is an external factor in cancer. The Western diet of African Americans in the United States is associated with a ye ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Division
Cell division is the process by which a parent cell (biology), cell divides into two daughter cells. Cell division usually occurs as part of a larger cell cycle in which the cell grows and replicates its chromosome(s) before dividing. In eukaryotes, there are two distinct types of cell division: a vegetative division (mitosis), producing daughter cells genetically identical to the parent cell, and a cell division that produces Haploidisation, haploid gametes for sexual reproduction (meiosis), reducing the number of chromosomes from two of each type in the diploid parent cell to one of each type in the daughter cells. Mitosis is a part of the cell cycle, in which, replicated chromosomes are separated into two new Cell nucleus, nuclei. Cell division gives rise to genetically identical cells in which the total number of chromosomes is maintained. In general, mitosis (division of the nucleus) is preceded by the S stage of interphase (during which the DNA replication occurs) and is f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
